This invention relates to a seat reclining apparatus for a vehicle which is arranged to adjustably fix an angle of a seat back relative to a seat cushion.
A vehicular seat reclining apparatus includes a body frame attached to a cushion arm of a seat cushion; a cover member attached to a back arm of a seat back, arranged to be pivoted relative to the base member, and including an internal tooth gear formed on an inner circumference surface of the cover member; and lock teeth attached to the body frame, and each having an external tooth gear. The relative pivot movement between the body frame and the cover member is restricted by the engagements between the external tooth gears of the lock teeth and the internal tooth gear of the cover member, so that the seat back is held in a predetermined angle position.
Recently, the thickness of the seat back becomes smaller. In a case in which the vehicular seat reclining apparatus provided between the cushion arm and the back arm has a large outside diameter (large external size), the vehicular seat reclining apparatus protrudes from an upper surface of the seat when the seat is in a full flat state. Therefore, it is required to decrease the outside diameter of the vehicular seat reclining apparatus.
In general, in a case in which the outside diameters (external sizes) of all of components are reduced for reducing the outside diameter (external size) of the seat reclining apparatus, the inside diameter of the internal tooth gear becomes small. Consequently, the tooth becomes small, and the strength decreases. In a case in which the number of the teeth reduces for reducing the outside diameter so as not to decrease the size of the tooth, and so as not to decrease the strength, the pitch angle of the pivot movement of the seat back with respect to the seat cushion becomes large when the external tooth gear is moved with respect to the internal tooth gear by one tooth. Therefore, it is required to reduce the outside diameter of the seat reclining apparatus without decreasing the strength, without increasing the pivot angle of the seat back by one tooth of the internal tooth gear.
A patent document 1 (Japanese Patent Application Publication No. 2008-18108) discloses, as a conventional vehicular seat reclining apparatus, a seat reclining apparatus including a body frame 5 connected with a seat cushion, a cover member 7 connected with a seat back, and a restricting member 8 through which the body frame 5 and the cover member 7 are held to be pivoted relative to each other, as shown in FIG. 1. An end portion of the restricting member 8 and an end portion of the body frame 5 are joined through welding bead 19 by the welding. Accordingly, in this conventional apparatus, it is unnecessary to provide a turned end portion of the restricting member 8 which is turned (bent) in a radially inner direction to cover an end surface of the body frame 5, as shown in FIG. 3. Therefore, it is possible to decrease a holding portion on the opposite side of the turned end portion, and thereby to decrease from S1 to S2, the radial size of a portion radially outside the outer circumference surface of the cover member 7. Therefore, it is possible to decrease the outside diameter of the vehicular seat reclining apparatus.